The sounds of gunfire and anger punctuated election day in the Democratic Republic of the Congo as millions of people got their second taste of democracy. Fears that violence would mar voting in one of Africa's biggest and most chaotic countries were realisedon Monday with reports of five killings as well as attacks on polling stations. This is Congo's second election since its 1998-2003 war.

Gunmen opened fire on a truck carrying voting materials in Lubumbashi, and later attacked voting centres, the interior minister, Bikanga Kazadi, told the Associated Press. The army was called in and a firefight left four assailants and one policeman dead, he added.

There were also logistical delays, claims of intimidation of voters and allegations of fraud as Congo held the second truly inclusive election in its history.

In West Kasai, locals burned down three polling stations and police fired shots to disperse around a hundred people who gathered outside the mayor's office in the town of Mbuji-Mayi, complaining they did not know were to vote.

One female election observer was seriously injured after being attacked by crowds claiming fraud in nearby Kananga, Francois Badibanga, spokesman for Congolese electoral monitoring organisation Renosec, told Reuters. "The situation is not good. We are in the hospital with our observer, she is between life and death," he said.Polling stations had been expected to open at 6am, but by Monday afternoon some precincts were still waiting for voting materials to be delivered, officials admitted. In the capital, Kinshasa, Human Rights Watch said weekend violence left nine dead and 76 injured, and rain meant people had to tread through mud along pot-holed roads on their journey to the polls. Voters complained of confusion over where they were meant to be voting due to polling stations being moved and errors with voter lists. There were also allegations of fraud and cheating.

At a school hosting a polling station in Kintambo district, the Guardian witnessed an election official being beaten by a furious mob who claimed he had tampered with presidential ballot papers. A policeman tried to intervene but shouting and physical aggression continued.

In Tshangu, where more than 1,500 candidates are running for 15 seats, there was an equally noisy and voluble crowd who pressed what they claimed were fake ballot papers to the windows of cars carrying election observers. Shreds of the papers were scattered about. Some complained that they had waited several hours or were not being allowed to vote at all.

Unemployed Julie Biuma, 41, with a baby tied to her back, said: "I came with a baby for nothing.

"Since six o'clock this morning I wanted to vote but they won't let me. I don't know what to do. It's really tough. The organisers made a lot of mistakes; there is disorder."

Denis Kipupa, 40, and unemployed, said: "It's badly organised today. Some people got here at 5am but voting started at 9am. There should be 28 ballot boxes here but there are only 16. We don't know where the other 12 are."

There was vocal support for Étienne Tshisekedi, the main challenger to president Joseph Kabila. "If Kabila is elected, we will put fire under everything," Kipupa added. " Tshisekedi is a lawyer ‚and he represents the rights of people."

Joel Tshiyombo, 20, who is unemployed, said: "We observe some cheating. If Kabila wins, we will kill each other because all the people don't like him. The people will not vote for him."

Elsewhere, in Gombe district, where Kabila cast his vote, the scene was much calmer, with people casting their votes in 15 minutes and describing the process as orderly.Jean-Pierre Okito, 45, a designer based in South Africa, said he had returned to vote for the first time in his life, choosing Kabila. "I've seen people voting in foreign lands but I couldn't vote, so I feel good for myself," he said. "It's been very well organised, no trouble, no push push. Anyone who says there is something wrong is a liar. We need international opinion to support young democracy in this country."

The station was visited by US diplomat Roger Meece, head of the UN peacekeeping mission in Congo. "I'm generally encouraged by what I see," he said.

"Obviously it's very important that everyone contributes to a peaceful election."I don't think the human mind can ever design a perfect system, but I'm very impressed by the system that's been put in place."

Ida Sawyer, of Human Rights Watch, said Kinshasa appeared to be quiet but there were allegations of fraud, ballot boxes being stuffed and selling of registration cards. There were also reports that eastern Congo voters were intimidated and told to vote for Kabila, she said.In the eastern city of Goma, Cindy McCain said that observers had stumbled upon what may be a case of ballot stuffing. The wife of US senator John McCain is part of a team of independent observers.

The polls - which pit Kabila against 10 rivals while more than 18,500 candidates compete for 500 seats in parliament - will test progress towards stability after decades of misrule and two wars in the last 15 years.